feat: Adds new decay system and SkipSerialization (#2311)

## Summary

- Replaces scan-based decay checking during world saves with an event-driven timer wheel scheduler
- Removes virtual property checks from serialization hot path, achieving 6-8x faster world saves

## Changes

### DecayScheduler (new):
- Timer wheel with 12 HashSet buckets (5-min intervals) + PriorityQueue for active processing
- O(1) register/unregister vs O(n) scan of all items
- Auto start/stop when items exist/empty
- Configurable tick interval with jitter to prevent system synchronization

### Item.cs:
- Added ScheduledDecayTime computed property
- Added UpdateDecayRegistration() called from SetLastMoved(), property setters, AddItem()/RemoveItem()
- Hooks in Visible, Movable, Spawner setters and Delete()

### World.cs:
- Removed _decayQueue, EnqueueForDecay(), ProcessDecay()
- ItemPersistence.Serialize() now tight loop without virtual calls

## Performance

| Metric        | Before     | After     | Improvement |
|---------------|------------|-----------|-------------|
| Items (230K)  | 245K ticks | 34K ticks | 8x faster   |
| Mobiles (43K) | 56K ticks  | 6K ticks  | 9x faster   |
| Total         | 302K ticks | 40K ticks | 7.5x faster |

## Configuration

decay.maxItemsPerTick = 250       # Items processed per tick
decay.tickInterval = 256ms        # Base processing interval
decay.bucketInterval = 5min       # Timer wheel bucket size
decay.jitterMaxMs = 25            # ±25ms tick jitter

Projects/UOContent/Engines/ConPVP/Games/BombingRun.cs

@@ -37,11 +37,13 @@ namespace Server.Engines.ConPVP
         {
         }
 
+        public override bool SkipSerialization => true;
+
         public override string DefaultName => "da bomb";
 
         public Mobile Thrower { get; private set; }
 
-        private Mobile FindOwner(IEntity parent)
+        private static Mobile FindOwner(IEntity parent)
         {
             if (parent is Item item)
             {
@@ -61,16 +63,6 @@ namespace Server.Engines.ConPVP
             base.Deserialize(reader);
 
             var version = reader.ReadInt();
-
-            switch (version)
-            {
-                case 0:
-                    {
-                        break;
-                    }
-            }
-
-            Timer.StartTimer(Delete); // delete this after the world loads
         }
 
         public override void Serialize(IGenericWriter writer)

Projects/UOContent/Engines/Plants/MiscItems/GreenThorns.cs

@@ -703,6 +703,8 @@ public partial class GreenThornsSHTeleporter : Item
 
     public override string DefaultName => "a hole";
 
+    public override bool SkipSerialization => true;
+
     public static void Create(Point3D location, Map map)
     {
         var tele = new GreenThornsSHTeleporter();
@@ -726,12 +728,6 @@ public partial class GreenThornsSHTeleporter : Item
         }
     }
 
-    [AfterDeserialization(false)]
-    private void AfterDeserialization()
-    {
-        Delete();
-    }
-
     private class InternalTimer : Timer
     {
         private readonly GreenThornsSHTeleporter _teleporter;

Projects/UOContent/Engines/Quests/Core/Items/HornOfRetreat.cs

@@ -115,6 +115,8 @@ public partial class HornOfRetreatMoongate : Moongate
 
     public override int LabelNumber => 1049114; // Sanctuary Gate
 
+    public override bool SkipSerialization => true;
+
     public override void BeginConfirmation(Mobile from)
     {
         EndConfirmation(from);
@@ -132,10 +134,4 @@ public partial class HornOfRetreatMoongate : Moongate
             Delete();
         }
     }
-
-    [AfterDeserialization(false)]
-    private void AfterDeserialization()
-    {
-        Delete();
-    }
 }

Projects/UOContent/Engines/Quests/Witch Apprentice/Mobiles/Zeefzorpul.cs

@@ -12,6 +12,8 @@ public partial class Zeefzorpul : BaseQuester
 
     public override string DefaultName => "Zeefzorpul";
 
+    public override bool SkipSerialization => true;
+
     public override void InitBody()
     {
         Body = 0x4A;
@@ -22,10 +24,4 @@ public partial class Zeefzorpul : BaseQuester
     public override void OnTalk(PlayerMobile player, bool contextMenu)
     {
     }
-
-    [AfterDeserialization(false)]
-    private void AfterDeserialization()
-    {
-        Delete();
-    }
 }

Projects/UOContent/Engines/Spawners/Commands/ShowSpawnerBordersCommand.cs

@@ -160,11 +160,7 @@ public partial class SpawnerBorder : ProjectedItem
         MinimumVisible = AccessLevel.Developer;
     }
 
-    [AfterDeserialization(false)]
-    private void AfterDeserialization()
-    {
-        Delete();
-    }
+    public override bool SkipSerialization => true;
 
     protected override bool SendEffect()
     {